I like the idea of an underdog among the MTF ranks, as it could explain a relatively small cast when MTFs tend to be platoon-sized at the least (to counter serious threats). The first scene threw me off at first, but it made sense in context.

I am iffy about the mentioning of other auditory SCPs, since it does not really add on to them and might seem like riding on those ideas to carry yours. What happens at the actual breach? What is going on there? I suppose there is a Part Two to this? If not, this feels like an Act One than a full performance.

I like the idea of an underdog among the MTF ranks, as it could explain a relatively small cast

It always felt to me like a sonic MTF wouldn't get the glory these days. There are some great world-ending auditory skips, but very few that are autonomously mobile. So once they have been captured / catalogued, there isn't much for an MTF to do any more. They were definitely larger in their glory days, which might get shown in another entry.

I am iffy about the mentioning of other auditory SCPs, since it does not really add on to them and might seem like riding on those ideas to carry yours

I would hope it doesn't come across that way. Other than 2337 (which I would be okay with losing if enough people think it's distracting) most of the other skips that breach containment aren't particularly well known. Also, multiple breaches are required and as noted above, there aren't many contenders that would require a response from Eta-11.

What happens at the actual breach? What is going on there? I suppose there is a Part Two to this?

If you look closely at the list of SCPs that breached, you'll see that most of the recontainment is probably quite straightforward, and might not make for an interesting story. However I'm working on a follow-up tale that does flow somewhat from this one, dealing with the aftermath of the breach. This is intended to be an introduction to the team.